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					                       The History and Importance of Impact Testing*

T. A. Siewert,1 M. P. Manahan,2 C. N. McCowan,3 J. M. Holt,4 F. J. Marsh,5 and E. A.
Ruth6

Reference: Siewert, T. A., Manahan, M. P., McCowan, C. N., Holt, J. M., Marsh, F.
J. and Ruth, E. A., "The History and Importance of Impact Testing," Pendulum
Impact Testing: A Century of Progress, ASTM STP 1380, T. A. Siewert and M. P.
Manahan, Sr., Eds., American Society for Testing and Materials, West Conshohocken,
PA, 1999.


Abstract: Charpy impact testing is a low-cost and reliable test method that is commonly
required by the construction codes for fracture-critical structures such as bridges and
pressure vessels. Yet, it took from about 1900 to 1960 for impact-test technology and
procedures to reach levels of accuracy and reproducibility such that the procedures could
be broadly applied as standard test methods. This paper recounts the early history of the
impact test and reports some of the improvements in the procedures (standard specimen
shape, introduction of a notch, correlation to structural performance in service, and
introduction of shrouds) that led to this broad acceptance.

Keywords: absorbed energy, Charpy impact testing, history, impact testing,
pendulum impact
1 Supervisory Metallurgist, Materials Reliability Division, National Institute of Standards and Technology,
Boulder, CO 80303.
2 President, MPM Technologies, Inc., 2161 Sandy Drive, State College, PA 16803.
3 Materials Research Engr., Materials Reliability Division, NIST, Boulder, CO 80303.
4 Alpha Consultants & Engineers, Pittsburgh, PA.
5 Retired (Bethlehem Steel), San Marcos, CA.
6 Tinius Olsen Test Machine Co., Willow Grove, PA.
* Contribution of NIST; not subject to copyright. Further details on the economic impact of Charpy impact
testing are included in a previous version of this report published in Standardization News, February 1999.
                    The History and Importance of Impact Testing

   Without uniformity of test results from day to day and from laboratory to laboratory,
the impact test has little meaning. Over the years, researchers have learned that the
results obtained from an impact test can depend strongly upon the specimen size and the
geometry of the notch, anvils, and striker. To a lesser degree, impact test results
also depend upon other variables such as impact velocity, energy lost to the test machine,
and friction. The goal of those who have written and modified ASTM Standard Test
Methods for Notched Bar Impact Testing of Metallic Materials (E 23) has over the years
been to standardize and control the variables associated with impact testing. This report
looks at the history of impact testing, with emphasis on the key advances in
understanding and application of the impact test, as reflected in the evolution of the test
standard.

Impact Testing: 1824 to 1895

    The earliest publication that we could find on the effects of impact loading on
materials was a theoretical discussion by Tredgold in 1824 on the ability of cast iron to
resist impulsive forces [1]. In 1849, the British formed a commission to study the use of
iron in the railroad industry, which began by considering practical approaches to impact
testing [2]. Apparently, failures of structures in the field were leading some researchers
to speculate that impact loads affected materials far differently than static loads, so
tensile-strength data (from slowly applied loads) was a poor predictor of performance
under dynamic loads.
    In 1857, Rodman devised a drop-weight machine for characterization of gun steels,
and over the subsequent 30-year period, his machine was widely used to test railroad
steels and for qualification of steel products [2]. Many of the early experiments with
impact tests were performed on final product forms, such as pipes or axles. Thus they
served as proof tests for a batch of material, or yielded comparative data for a new
product design, or basic reference data on the impact resistance of different construction
materials (such as the comparison of wrought iron to ductile iron). Instrumentation was
poor for the early impact tests, so the data is often only as break or no-break for a mass
dropped through a certain distance. These early drop weight tests were conducted using
smooth (no notch or crack starter) rectangular bars. While the test worked well for brittle
materials, where crack initiation is easy, specimens of ductile materials often just bent.
LeChatalier introduced the use of notched specimens while conducting drop-weight tests
in 1892 [3]. He found that some steels that showed ductile behavior (bending without
fracture) in a smooth rectangular bar, would exhibit fragile behavior when the test
specimen was notched. While the addition of a notch was a major improvement in the
test method, a test procedure was needed that would provide a continuous, quantitative
measure of the fracture resistance of materials. Also, substantial work was needed to
develop test procedures that produced consistent data, and to answer the objections of
those who doubted the value of impact testing.

1895 to 1922
    This period saw the establishment of a number of national and international standards
bodies, which took up the causes of developing robust test procedures and developing
consensus standards for many technologies, including impact testing. One of these
standards bodies was The American Society for Testing and Materials, established in
1898. Another was the International Association for Testing Materials, officially
established in 1901, but this association grew out of the good response to two previous
International Congresses that had been held a number of years before. These two
standards bodies seem to have had a good working relationship, and the President of
ASTM, Prof. H. M. Howe, also served on the Board of IATM during this time [4].
    In 1902, only four years after the founding of ASTM, the ASTM "Committee on the
Present State of Knowledge Concerning Impact Tests" published a bibliography on
impact tests and impact testing machines in the second volume of the Proceedings of
ASTM [5]. This bibliography listed more than 100 contemporary papers on impact
testing published in the U.S., France, and Germany. Many of these papers contained
information that was also known to the members of IATM. In fact, some of the papers
had been presented and discussed at the IATM Congresses.
    Among the references is a report by Russell (published in 1898 and reprinted in this
STP) that shows remarkable insight into the needs of the design engineers of the time and
introduces quantitative measurement to the test [6]. He pointed out that none of the
machines of the time, typically of a drop-weight design, had the ability to determine any
data beyond whether the specimen broke or remained intact. Therefore, he designed and
built a pendulum machine which "would measure the energy actually absorbed in
breaking the test bar". His report shows a test machine that is based on the same
swinging pendulum concept as those in common use today and mentions his careful
analysis of the mechanics of the test, including corrections for friction losses and
calculation and comparison of the centers of gravity and percussion. Since this was
before the time of compact, standardized test specimens, the machine was vary large and
massive, and was capable of breaking many full-size products. Besides showing a
prototype of the machines used today, this report is valuable in that it includes data on
over 700 tests of typical construction materials, and emphasizes the effect of the rate of
loading in evaluating materials for different service conditions. Russell's pendulum
impact machine finally provided a means for quantifying the energy absorbed in
fracturing a test specimen for a wide range of materials and conditions. His paper nicely
summarizes the test-machine technology and knowledge for material performance at the
end of the past century, and so served as a benchmark for future research. To the best of
our knowledge, Russell was the first to develop and demonstrate the advantages of the
pendulum design for impact testing machines.
    The members of IATM Commission 22 (On Uniform Methods of Testing Materials)
continued to conduct research that addressed the shortcomings in the impact testing
techniques, until they had developed a knowledge of most of the important factors in the
test procedure. Even though many of these early machines and reports are simplistic by
today’s standards, they provided previously unknown data on the impact behavior of
materials. France seems to have been an early adopter of impact testing for infrastructure
construction standards, and so French researchers provided much data on the effects of
procedure variables and were the most prolific contributors to the IATM Proceedings
between 1901 and 1912. Incidentally, it was a representative from France, G. Charpy,
who became the chair of the impact testing activity after the 1906 IATM Congress in
Brussels, and presided over some very lively discussions on whether impact testing
procedures would ever be sufficiently reproducible to serve as a standard test method [7].
Charpy’s name seems to have become associated with the test because of his dynamic
efforts to improve and standardize it, both through his role as Chairman of the IATM
Commission and through his personal research [8]. He seems to have had a real skill for
recognizing and combining key advances (both his and those of other researchers) into
continually better machine designs and consensus procedures. For example, Charpy
acknowledges the benefits of Russell's pendulum design in his 1901 paper [8] by stating:
"Russell described in a paper presented in 1897 at the American Society of Civil
Engineers some 'experiments with a new machine for testing materials by impact.' The
machine he is using is designed to determine the work absorbed by the rupture of a bar,
for this, the ram used appears in the form of a pendulum arranged in such a way so that
when it is released from its equilibrium position, it meets the test bar in passing through
the vertical position, breaks it and afterward rises freely under the influence of the
acquired speed. The difference between the starting height and the finishing height of the
pendulum allows evaluation of the work absorbed by the rupture of the bar."
    By 1905, Charpy had proposed a machine design that is remarkably similar to present
designs and the literature contains the first references to "the Charpy test" and "the
Charpy method". He continued to guide this work until at least 1914 [7,9-10]. A number
of other standard machine designs and procedures were also under consideration at this
time, and in 1907 the German Association for Testing Materials adopted one developed
by Ehrensberger [10]. Because the pendulum machine had not achieved dominance yet,
impact machine designers and manufacturers offered three major types; Drop Weight
(Fremont, Hatt-Turner, and Olsen), Pendulum Impact (Amsler, Charpy, Dow, Izod,
Olsen, and Russell), and Flywheel (Guillery).
    This was a period during which the configuration and size of specimens closely
approached what we use today [7]. Originally, two standard specimen sizes were most
popular. The smaller had a cross section of 10 by 10 mm, a length of about 53 mm (for a
distance of 40 mm between the points of support), a notch 2 to 5 mm deep, and a notch
tip radius near 1 mm. The larger and initially more popular of these specimen sizes was
scaled up by a factor of three in all these dimensions. The group favoring the larger
specimen pointed out the advantage of sampling a larger cross section of the material (for
reduced scatter in the data) and the difficulty of producing the small notch radius on the
smaller specimen. However, the group favoring the smaller specimen eventually won
because a more compact and lower-cost machine could be used, and not all structures
were thick enough to produce the larger specimen. Besides specimen dimensions that are
very similar to what we use today, the Commission proposed features for a standard
impact procedure that included:

   -   limits for the velocity of the striker,
   -   rigid mounting to minimize vibration losses,
   -   a minimum ratio of anvil mass and rigidity to striker size, and
   -   recognition of the artificial increase in energy as ductile specimens deform around
       the edges of a wide striker [7].

One report at the 1912 meeting [7] included the testimonial from a steel producer of how
the improved impact test procedures had allowed them to tailor the refining processes to
produce less brittle steel. The report describes a reduction by a factor of 20 in the number
of production parts that were rejected for brittle performance.


1922 to 1933: The Beginning of ASTM Method E 23

    ASTM Committee E-1 on Methods for Testing sponsored a Symposium in 1922 on
Impact Testing of Materials as a part of the 25th Annual Meeting of the Society, in
Atlantic City, New Jersey. The Symposium included a history of the developments in
this area, a review of work done by the British Engineering Standards Association,
several technical presentations, and the results of a survey sent to 64 U.S. testing
laboratories [11]. Twenty-three respondents to the survey offered detailed information on
topics such as the types of machines in use, the specimen dimensions, and procedures. In
addition, many responded positively to a question about their willingness to develop an
ASTM standard for impact testing.
    Based on the information in this survey, an ASTM subcommittee began to prepare a
standard test method for pendulum impact testing in 1923. This effort took until 1933,
when ASTM published "Tentative Methods of Impact Testing of Metallic Materials,"
ASTM designation E 23-33T. (An ASTM specification of “Tentative” indicated that it
was subject to annual review and was a work in progress. The tentative designation is no
longer used by ASTM.) (Other countries also developed their own standards; however,
we found it difficult to find their records and to track their developments.)
    ASTM E 23-33T specified that a pendulum-type machine was to be used in testing and
“recognized two methods of holding and striking the specimen”, that is, the Charpy test
and the Izod test (where the specimen is held vertically by a clamp at one end). It did not
specify the geometry of the striking edge (also known at the time as the “tup”) for either
test. It stated that “the Charpy type test may be made on unnotched specimens if
indicated by the characteristics of the material being tested, but the Izod type test is not
suitable for other than notched specimens”. Only a V-notch was shown for the Charpy
test. Although the dimensions for both types of specimens were identical with those
currently specified, many tolerances were more restrictive. The units were shown as
English preferred, metric optional. The committee pointed out many details that
influence the test results, but because they did not have the knowledge and database
needed to specify values and/or tolerances for these details, the document was issued as a
tentative. The original document contains an appendix with general discussions of
applications, the relation to service conditions, and comparisons between materials. As
our understanding of the variables in Charpy testing has grown, ASTM E 23 has been
revised repeatedly to incorporate the new knowledge.

1934 to 1940
   The first revision of E 23 was issued in 1934 and it added a dimension for the radii of
the anvil and specifically stated that “these specimens (both the Charpy and the Izod) are
not considered suitable for tests of cast iron” referencing a report of ASTM Committee
A3 on Cast Iron. The method retained the “tentative” designation.
   The geometry of the Charpy striking tup, specifically the radius of the tup that
contacted the specimen, was not specified in the 1934 revision. However, the minutes of
the 1939 and 1940 meetings for the Impact Subcommittee of E1 state that this item was
discussed and a survey was made of the geometries used in the United Kingdom and in
France. Those countries had been using radii of 0.57 mm and 2 mm, respectively. For
reasons that were not recorded, the members of the Subcommittee agreed to a radius of 8
mm at the 1940 meeting and ASTM E 23 was revised and reissued as E 23-41T. Two
other changes that occurred with this revision were that metric units became the preferred
units, and keyhole and U notches were added for Charpy-test specimens.

1940 to 1948

    Impact testing seems to have been a useful technique for evaluating materials, but was
not a common requirement in purchase specifications and construction standards until the
recognition of its ability to detect the ductile-to-brittle transition in steel. Probably the
greatest single impetus toward implementation of impact testing in fabrication standards
and material specifications came as a result of the large number of ship failures that
occurred during World War II. These problems were so severe that the Secretary of the
U.S. Navy convened a Board of Investigation to determine the causes and to make
recommendations to correct them. The final report of this Board stated that of 4694
welded-steel merchant ships studied from February 1942 to March 1946, 970 (over 20%)
suffered some fractures that required repairs [12]. The magnitudes of the fractures ranged
from minor fractures that could be repaired during the next stop in port, to 8 fractures that
were sufficiently severe to force abandonment of these ships at sea. Remedies included
changes to the design, changes in the fabrication procedures and retrofits, as well as
impact requirements on the materials of construction. The time pressures of the war
effort did not permit thorough documentation of the effect of these remedies in technical
reports at that time; however, assurance that these remedies were successful is
documented by the record of ship fractures that showed a consistent reduction in fracture
events from over 130 per month in March 1944 to less than five per month in March
1946, even though the total number of these ships in the fleet increased from 2600 to
4400 during this same period [12].
    After the war, the National Bureau of Standards released its report on an investigation
of fractured plates removed from some of the ships that exhibited these structural failures
and so provided the documentation of the importance of impact testing [13]. The NBS
study included chemical analysis, tensile tests, microscopic examination, Charpy impact
tests, and reduction in thickness at the actual ship fracture plane. A notable conclusion of
the report was that the plates in which the fracture arrested had consistently higher impact
energies and lower transition temperatures than those in which the fractures originated.
This was particularly important because there was no similar correlation with chemical
composition, static tensile properties (all steels met the ABS strength requirements), or
microstructure. In addition, the report established 15 ft-lb (often rounded to 20 J for
metric requirements) as a minimum toughness requirement, and recommended that "some
criterion of notch sensitivity should be included in the specification requirements for the
procurement of steels for use where structural notches, restraint, low temperatures, or
shock loading might be involved", leading to a much wider inclusion of Charpy
requirements in structural standards.


1948 to Present

    By 1948, many users thought that the scatter in the test results between individual
machines could be reduced further, so additional work was started to more carefully
specify the test method and the primary test parameters. By 1964, when the ASTM E 23
standard was revised to require indirect verification testing, the primary variables
responsible for scatter in the test were well known. In a 1961 paper, Fahey [14]
summarized the most significant causes of erroneous impact values as follows: (1)
improper installation of the machine, (2) incorrect dimensions of the anvil supports and
striking edge, (3) excessive friction in moving parts, (4) looseness of mating parts, (5)
insufficient clearance between the ends of the test specimen and the side supports, (6)
poorly machined test specimens, and (7) improper cooling and testing techniques. While
the machine tolerances and test techniques in ASTM E 23 addressed these variables, it
was becoming apparent that the only sure method of determining the performance of a
Charpy impact machine was to test it with standardized specimens (verification
specimens).
    Much of the work that showed that impact tests did not have inherently high scatter,
and could be used for acceptance testing, was done by Driscoll at the Watertown Arsenal
[15]. Driscoll’s study set the limits of 1 ft-lb (1.4 J) and ± 5%, shown in Figures 1 and 2.
The data superimposed on these limits in Figures 1 and 2 are the initial verification
results gathered by Driscoll for industrial impact machines to evaluate his choice of
verification limits. In Figure 1, the verification results for the first attempt on each
machine are shown: only one machine fell within the ± 1 ft-lb (1.4 J) limit proposed for
the lower energy range. Results for retests on the same machines after maintenance are
shown in Figure 2. Driscoll’s work showed the materials testing community that not all
machines in service could perform well enough to meet the indirect verification
requirements, but that most impact machines could meet the proposed requirements if the
test was conducted carefully and the machine was in good working condition. With the
adoption of verification testing, it could no longer be convincingly argued that the impact
test had too much inherent scatter to be used as an acceptance test.
    Early results of verification testing showed that 44% of the machines tested for the
first time failed to meet the prescribed limits, and it was thought that as many as 50% of
all the machines in use might fail [16]. However, the early testing also showed that the
failure rate for impact machines would drop quickly as good machines were repaired, bad
machines were retired, and more attention was paid to testing procedures. It was
estimated that approximately 90% of the machines in use could meet the prescribed limits
of ± 1 ft-lb (1.4 J) or ± 5%. Recently acquired verification specimen data, shown in
Figures 3 through 5, confirm these predictions. Failure rates for verification tests at low,
high, and super-high energy ranges are currently estimated to be 12, 7, and 10%,
respectively [17].
   Overall, the incorporation of verification limits in ASTM E 23 has greatly improved
the performance of impact machines, so that data collected using ASTM E 23 machines
can be compared with confidence. ASTM E 23 is still the only standard in the world, to
our knowledge, that requires very-low-energy impact specimens (between 15 and 20 J)
for verification, and as shown by the data in Figure 1, results obtained using machines in
need
of maintenance can vary by more than 100% at this energy level. In effect, the limits
imposed by ASTM E 23 have produced a population of impact machines that are
arguably the best impact machines for acceptance testing in the world.
   While ASTM E 23 is used around the world, there are other forums for the
development of global standards. One of these, the International Organization for




                     40

                     30

                     20

                     10

                       0

                     -10
                        0      20     40 60 80             100 120
                                        Energy, J

Standardization, ISO, allows qualified representatives from all over the world to come
Figure 1 - The deviation in the resolution of global standardization problems [18].
together as equal partners and energy values obtained for the first round of tests on ISO
industrial machines. The deviation is calculated as Testing, and its Subcommittee SC 4
Committee TC 164 handles the topic of Mechanical the difference between the results of
the Watertown Arsenal machines this subcommittee has developed and maintains
handles toughness testing. While and the industrial machines. These data were ten
originally published by D.E. Driscoll, Reproducibility of Charpy Impact Test, ASTM STP
176, 1955.
       standards on toughness testing, perhaps the most pertinent is ISO Standard R 442:1965
       Metallic Materials - Impact Testing - Verification of Pendulum Impact Machines. This
       standard covers the Charpy test and is presently undergoing balloting for revision. An




                     10
                       8
                       6
                       4
                       2
                       0
                      -2
                      -4
                      -6
                      -8
                        0       20       40     60    80          100 120
                                              Energy, J



Figure 2 - The deviation and energy values for the second and third rounds of tests on industrial
machines. The data shows that all but two of the machines tested were able to pass the 1.4 J or 5%
criteria after appropriate repairs were made. These data were originally published by D. E. Driscoll,
Reproducibility of Charpy Impact Test, ASTM STP 176, 1955.

       important feature of this document is that it recognizes Charpy testing with both the 2-
       mm and 8-mm radius striker. There are other regional and national standards that specify
       impact testing procedures, such as the Japanese standard, JIS Z2242, Method for Impact
       Test for Metallic Materials.
       Typical Applications Today
Nuclear

    Since it is impractical to measure the fracture toughness of large specimens throughout
the life of a nuclear power plant, surveillance programs use Charpy and tensile specimens
to track the embrittlement induced by neutrons. The economic importance of the Charpy
impact test in the nuclear industry can be estimated by noting that most utilities assess the
outage cost and loss of revenue for a nuclear plant to be in the range of $300,000 to
$500,000 per day. If Charpy data can be used to extend the life of a plant one year
beyond the initial design life, a plant owner could realize revenues as large as
$150,000,000. Further, the cost avoidance from a vessel related fracture is expected to be
in the billion-dollar range. To date, the NRC has shut down one U.S. plant as a result of
Charpy data trends. It is important to note that this plant's pressure vessel was
constructed from a one-of-a-kind steel and is not representative of the U.S. reactor fleet.
Figure 4 - Distribution of high energy verification data. Data for 1995-1997. Approximately
2400 tests. Each test is an average of five specimens. The vertical lines at ±5% represent the
                                       low-energy verification data. Data for
            Figure 3 - Distribution of acceptance criteria.
            1995-1997. Approximately 2400 tests; each test is an average of five
            specimens. The vertical lines at ±1.4 J represent the acceptance
            criteria.
                                                                                    400
                                                                                     600

                                                                                     500
                                                                                    300
Nonetheless, with decisions like this based on the Charpy test, the importance of ASTM
E 23 and the restraints it applies cannot be overemphasized.

Steel

   The Charpy V-notch (CVN) test specimen and associated test procedure is an effective
cost-saving tool for the steel industry. The specimen is relatively easy to prepare, many
specimens can be prepared at one time, various specimen orientations can be tested,
and relatively low-cost equipment is used to test the specimen. In many structural steel
applications, the CVN test can be used: (1) as a quality control tool to compare different
heats of the same type of steel, (2) to check conformance with impact requirements in
standards, and (3) to predict service performance of components. Also, CVN test
information can be correlated with fracture toughness data for a class of steels so that the
results of fracture-mechanics analyses can be compared with the material toughness.
     Figure 5 - Distribution of the super-high energy verification data.
     Data for 1995-1997. Approximately 650 tests. Each test is an
     average of five specimens. The vertical lines at ±5% represent the



                                                                                        150
     acceptance criteria.


   CVN data have many uses, such as during the design and construction of a bridge or
an offshore oil platform. Before full-scale production of the steel order can begin, the
supplier needs to demonstrate to the buyer that the steel plate is capable of meeting
certain design criteria. The process begins by making the steel grade and then testing a
portion of the plate to determine if all required criteria are met. Also, steel mill
equipment imposes limitations on plate size; therefore, individual steel plates need to be
welded together in the field to produce lengths which can reach deep into ocean waters.
Small sections of the sample plate are welded together, and fracture mechanics tests are
conducted to determine the crack tip opening displacement (CTOD) toughness in the heat
affected zone (HAZ) and in areas along the fusion line where the weld metal meets the
base metal. Then, a steel supplier might correlate the CTOD test results with CVN 50%
ductile-brittle transition temperature (DBTT). By agreement between the customer and
supplier, this correlation can allow the steel supplier to use the Charpy test instead of the
more expensive and time-consuming CTOD testing.

Continuing Standardization Efforts
    Even after 100 years, the Charpy impact test procedures still have room for
improvement. The ASTM E 23 standard has recently been redrafted to provide better
organization and to include new methods such as in-situ heating and cooling of the test
specimens. Two new related standards are also under development through ASTM Task
Group E 28.07.08, “Miniature and Instrumented Notched Bar Testing”, which was
formed a little more than two years ago. The first standard covers miniature notched bar
impact testing and relies on many of the existing practices related to test machine
requirements and verification as specified in existing standard E 23. The second standard
is focused on instrumented testing, where strain gages attached to the striker provide a
force-deflection curve of the fracture process for each specimen. Research is focused on
using these data to obtain plane strain fracture toughness as well as other key test
parameters. Upon acceptance of the standard by ASTM, both the existing E 23 standard
and the new miniature notched bar standards would reference the instrumented impact
standard.
    The state of the art in impact testing continues to advance in other parts of the world
also. ISO is balloting a standard (14556) on instrumented impact testing, there is work in
Europe on miniature Charpy specimens, and ESIS is investigating the use of pre-cracked
Charpy specimens for determining fracture toughness. It can be expected that
harmonization efforts will bring some of this work into E 23 in the future.


Conclusion

    The ASTM E 23 standard is a document that continues to improve as our technical
knowledge increases. Several years ago, at the ASTM Symposium on “The Charpy
Impact Test: Factors and Variables” [19], a bystander was overheard to say: “I see that
there is a Symposium on the Charpy Test; what can be new there?” Since then, the
document has been updated twice and is currently being revised to reflect new
developments and to make it more “user friendly.” Although ASTM E 23 has been a
useful standard for many years, it continues to be a “work in progress,” a work used
extensively to help evaluate existing and new materials for products and structures -- a
test to ensure safety as well as to reduce the initial and lifetime costs for structures.
Knowledge which will help make the test more accurate and reliable is continually being
gained. New technologies such as miniaturization of the test, instrumenting the striker to
obtain additional data, and developing mechanics models to enable extraction of plane
strain fracture toughness will be areas of development over the next 100 years. We
anticipate that the benefits from the application of E 23 during the next 100 years will
overshadow the benefits from those in the past 100 years.

References

[1]    Tredgold, T., Strength of Cast Iron, 1824, pp. 245-268.

[2]    White, A.E. and Clark, C.L., Bibliography of Impact Testing, Department of
       Engineering Research, University of Michigan, 1925.
[3]    LeChatalier, A., “On the Fragility After Immersion in a Cold Fluid”, French
       Testing Commission, Volume 3, 1892.

[4]    "Report on the Work of the Council from the Budapest to the Brussels Congress -
       1901-1906," Proceedings of the International Association for Testing Materials,
       Brussels Congress, 1906.

[5]    Hatt, W.K. and Marburg, E., "Bibliography on Impact Tests and Impact Testing
       Machines," Proceedings ASTM, Vol. 2, 1902, p. 283.

[6]    Russell, S. B. "Experiments with a New Machine for Testing Materials by
       Impact," Transactions ASCE, Vol. 39, June 1898, p. 237.

[7]    Proceedings of the Sixth Congress of the International Association for Testing
       Materials, New York, 1912.

[8]    Charpy, M.G., "Note sur l'Essai des Metaux a la Flexion par Choc de Barreaux
       Entailles, Soc. Ing. Francais, June 1901, p. 848.

[9]    "Impact Testing of Notched Bars," The Engineer, Vol. 99, March 10, 1905 pp.
       249-250.

[10]   Whittemore, H. L., "Resume of Impact Testing of Materials, with Bibliography,"
       Proceedings ASTM, Vol. 22, Part 2, 1922, p. 7.

[11]   Warwick, C. L., "Resume on Notched Bar Tests of Metals," Proceedings of
       ASTM, Vol. 22, Part 2, 1922, p. 78.

[12]   The Design and Methods of Construction of Welded Steel Merchant Vessels:
       Final Report of a (U.S. Navy) Board of Investigation, Welding Journal, Vol. 26,
       No. 7, July 1947, p. 569.

[13]   Williams, M. L. and Ellinger, G. A., Investigation of Fractured Steel Plates
       Removed from Welded Ships, National Bureau of Standards Report, December 9,
       1948.

[14]   Fahey, N. H., "Effects of Variables in Charpy Impact Testing," Materials
       Research Standards, Vol. 1, No. 11, Nov., 1961.

[15]   Driscoll, D. E., "Reproducibility of Charpy Impact Test," Impact Testing, ASTM
       STP 176, 1955.

[16]   Fahey, N. H., "The Charpy Impact Test - Its Accuracy and Factors Affecting Test
       Results," Impact Testing of Metals, ASTM STP 466, ASTM, 1970.
[17]   McCowan, C. N., Wang, C. M., and Vigliotti, D. P., "Summary of Charpy Impact
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       Evaluation, 1998.

[18]   More information is on the ISO World Wide Web site, at http://www.iso.ch

[19]   Charpy Impact Test: Factors and Variables, ASTM STP 1072, J. M. Holt, Ed.,
       ASTM, 1990.